This invention relates to the bending of a glass sheet or a stack of glass sheets by heating the glass sheet(s) placed on a bending mold to cause sagging of the softened glass sheet(s), and more particularly to a carriage for supporting thereon the bending mold and carrying the mold with the glass sheet(s) placed thereon into a shaping zone of a furnace, the carriage having means to locally intensely heating the glass sheet(s).
For producing a curved glass sheet member such as an automobile window glass, one of the conventional methods of bending a glass sheet to a desirerably curved shape is the sag bending method. By this method the glass sheet is horizontally placed on a bending mold, usually a female mold, and heated to a temperature near to the softening point of the glass so that the softened glass sheet sags and bends in conformance with the shaping surface of the mold. Usually the bending mold is mounted on a carriage, which travels along a predetermined path through a furnace to allow the glass sheet lying thereon to be sufficiently heated before entering the shaping zone of the furnace. In the case of producing a curved and laminated glass member, the two glass sheets to be laminated are placed on the bending mold as a stack with application of a releasing agent at the interface between the two glass sheets, and the two glass sheets are bent simulataneously in the above manner.
When it is required to relatively sharply bend the glass sheet in its selected and limited areas than in the major region it is usual to locally intensely heat the glass sheet in its selected regions by using auxiliary heaters provided to the furnace. In this regard it is known to fixedly attach heaters to the mold carriage at such locations that selected areas of the glass sheet lying on the mold may be intensely heated from the downside. However, it is difficult to attach heaters to the mold carriage so as to locally heat the glass sheet on the mold from the upside.
JP-A 59-162142 proposes to locally intensely heat a glass sheet to be bent by providing the shaping furnace with a swingably suspended arm which holds a heater element to heat a specified area of the glass sheet from the upside. JP-A 62-41728 proposes to locally intensely heat a glass sheet travelling through a furnace from the upside by moving suspended heating means such as gas burners along the path of the travel of the glass sheet. However, these proposals entail complicated mechanisms and troublesome operations.